Geologic Column: Beer's secret ingredient: geology

Geologists have a long history with beer. Earlier this year, I decided to raise my own beer appreciation to the next level and take a class on the subject. I attended the beer school at the Anheuser-Busch Brewery in St. Louis. A few minutes into the class, our instructor noted that the beer-brewing process uses clean water, which, he said, is basically the same no matter where you are. Unfortunately, that got us off on the wrong foot. As anyone in the beer business should know, water — and what’s in the water, courtesy of the geology through which it percolates — can make all the difference in an end product.

The dissolved minerals in water can make a beer outstanding — or undrinkable. For example, calcium is critical for yeast to work effectively. It also controls the pH of the mash and aids with coagulation and flocculation. Hence, distilled water won’t work for beer.

Think about the regions known for certain beers. I guarantee that the primary reason for each association is the water. After all, beer is more than 90 percent water. You can’t brew a pilsner (at least not a very good one) with water from Dublin (115 parts per million [ppm] calcium, 319 ppm bicarbonate and 53 ppm sulfate), or a stout in the Pilsen region of the western Czech Republic (7 ppm calcium, 3 ppm bicarbonate and virtually no sulfates). In general, areas with softer water produce lagers and darker ales, while those with harder, more mineral-rich water are more conducive to paler, hoppier ales.

Too much iron in the water? The beer can develop a metallic flavor. High levels of zinc? The beer may be cloudy — and too much zinc can be toxic to yeast. Want to taste more hops? Try adding gypsum. The area around Burton-upon-Trent, northwest of London, England, has a high salt content from the gypsum in the subsurface, and the sulfate enhances the flavor of hops. In fact, the process of adding gypsum to water in order to brew a pale ale is known as “Burtonisation.” At its peak in the 19th century, the Burton area had 30 breweries; the pale ale produced there was stable as a result of the preserving characteristics of the sulfates, allowing the beer to survive shipping, even as far as India. That’s where the name “India Pale Ale,” or IPA, came from. You can thank the gypsum — and the geology — for that.

After mergers, acquisitions and changes in the global economy, Burton now has fewer than a dozen breweries. Coors is one of them, but the beer it produces there is unlikely to resemble that brewed from the “pure Rocky Mountain spring water” from Coors’ native Golden, Colo. The natural water in nearby Denver (31.5 ppm calcium, 104 ppm bicarbonate and 50.8 ppm sulfate) is distinctly different from the Burton water (295 ppm calcium, 300 ppm bicarbonate and 725 ppm sulfate). (One of the other major breweries in Burton is the umbrella company that owns Anheuser-Busch.)

Today, the brewing world has a robust supply of geologic materials that can be added to local waters to reproduce virtually any native source. Home brewers can purchase minerals like calcium carbonate, gypsum, and “water crystals” (66 percent calcium sulfate and 34 percent magnesium sulfate) that will, in the proper proportions, emulate native waters from anywhere in the world. “Burton Water Salts,” for example, offer a concoction that sounds like a magic potion, including “calcium for hardness, magnesium for yeast nutrition, and the chloride ions [to] impart a more full-bodied beer” (description courtesy of Midwest Supplies).

Ultimately, however, there is no substitute for natural waters, which heavily depend on local geology for their unique characteristics, and the character of the natural water used can have a big impact on the final brew. In fact, with the availability of malted barley, hops and yeast from around the planet, the water is often the only local ingredient in beer. The metamorphic rocks underlying Pilsen allow groundwater to move through fractures, but not many minerals are dissolved. The limestone around Dublin produces groundwater with a very different composition. And the water near Burton-upon-Trent is influenced by the underlying sandstone with gypsum.

Getting back to our beer school instructor, when I asked about the effect of minerals dissolved in the water, he admitted that he was not familiar with the scientific details. I am sure, though, that the beer-makers themselves are acutely aware.

I have now joined the ranks of many of my geologist friends in having a greater appreciation of the subtleties of beer — and the geology behind it. (I have a beer school certificate to prove it!) And although I don’t know for certain to what type of brew the soft water in the Atlanta region (10 ppm calcium, 26 ppm bicarbonate and 6 ppm sulfate) best lends itself, like any good geologist, I’d be more than happy to do some taste testing to find out.